Roundup Ready soybean gene concentrations in field soil aggregate size classes.

Area of Science:

• Agricultural biotechnology
• Environmental microbiology
• Soil science

Background:

• Roundup Ready (RR) soybeans possess genes for glyphosate herbicide tolerance.
• Widespread cultivation of RR soybeans raises concerns about environmental DNA persistence.
• Recombinant DNA in soil may pose risks for genetic transformation of soil bacteria.

Purpose of the Study:

• To quantify recombinant DNA concentration in different soil aggregate sizes.
• To investigate the role of soil aggregates in the persistence of glyphosate-tolerance genes.
• To assess the distribution of CP4 5-enol-pyruvyl-shikimate-3-phosphate synthase (cp4 epsps) DNA in soil.

Main Methods:

• Real-time PCR was employed to detect and quantify the cp4 epsps gene.
• Soil samples were fractionated into four aggregate size classes: >2000 µm, 2000–500 µm, 500–250 µm, and <250 µm.
• Gene concentrations were compared across these aggregate size fractions.

Main Results:

• Significantly higher concentrations of cp4 epsps DNA were found in larger soil aggregates (>2000 µm).
• The >2000 µm aggregate fraction, representing ~30% of the soil mass, contained 66.62% to 99.18% of the total detected gene copies.
• Recombinant DNA was disproportionately concentrated in the largest soil aggregates.

Conclusions:

• Soil aggregate structure influences the distribution and potential persistence of recombinant DNA from genetically modified crops.
• Larger soil aggregates (>2000 µm) act as significant reservoirs for cp4 epsps DNA.
• Aggregate formation may play a crucial role in the environmental fate of recombinant DNA in agricultural soils.